Subwoofer Reviews

"Subwoofers are boring," whined John Atkinson when we were dickering about column inches for my review of the Thiel CS2.4 loudspeaker in this issue. "I know they're important, but I just don't get excited reading about them."

It didn't seem like such a big deal. After all, when designer Kevin Voecks added a passive radiator to the bottom of Revel Loudspeakers' powerful Ultima Sub 15 subwoofer, no one expected that the resulting 6dB increase in bass output below 35Hz would be so audible. However, Revel's sophisticated double-blind listening tests (described in my review of their flagship Ultima Salon full-range loudspeaker in the March 1999 Stereophile, revealed that a big change had occurred. With now twice the radiating surface, the modified Sub 15 produced significantly deeper, more powerful bass.

Makers of powered subwoofers fall into two camps: those that fit a high-powered amplifier and a single, large woofer into a relatively small, unobtrusive enclosure; and those that build two or more 10" woofers and an amp of moderate power into a larger, heavier enclosure.

Harry Partch (1901-1974), composer and inventor of musical instruments, delighted in generating deep bass. Finding most standard orchestral instruments wanting in that department, he built the huge Marimba Eroica, which he described on his A Glimpse into the World of Harry Partch: 27 Unique Instruments (LP, Columbia MS-20576):

"You certainly love weird music!" my wife yelled from the kitchen. This just reconfirmed my suspicion that reviewing subwoofers is a lonely job that brings no respect. What's so weird about the droning of Tibetan temple horns accompanied by the chants of Tibetan Gyuto monks, all framed by a powerful synthesizer in Philip Glass's soundtrack to Kundun (CD, Nonesuch 79460-2)? What's so strange about the karate-like cries of the drummers in the Kromata Percussion ensemble as they smash away at their timpani and gongs in Yoshihisa Taira's Hierophonie V (CD, BIS CD-232)? What's so odd about the shuddering majesty of 25Hz notes played by Harry Partch's one-of-a-kind Eroica Marimba, heard on his Delusion of the Fury (LP, Columbia M2 30576)? Why would any spouse object to the primitive, driving synthesizer growls and screams from Morton Subotnick's The Wild Bull (LP, Nonesuch H-71208)?

It's common to read ads for new audio hardware that crow about "revolutionary" breakthroughs in sound performance, and that's how Velodyne crowed about their new Digital Drive DD-18, servo-controlled, powered 18" subwoofer. The ads suggested that the DD-18 can be digitally equalized to one's room with a resultant in-room frequency response of 20-200Hz, ±3dB.

Émile Durkheim (1858-1917) once wrote, "The less limited one feels, the more intolerable all limitation appears" (footnote 1). Although directed at the paradoxical observation that suicide rates are higher in newly prosperous countries than in those mired in poverty, his comment applies equally well to subwoofers.

"You can't get deep bass in your room," a reviewer from another magazine who'd never visited my room insisted recently on the phone. "Do you know how long a 20Hz bass wave is? It's 40 feet long, and your room is tiny."

From The Audio Catechism:Q: What is a subwoofer?A: A large, ugly device that must be placed in the most inconvenient location in the listening room—for instance, in front of the only door.Q: What is the purpose of the subwoofer?A: To produce prodigious amounts of low-frequency sound and to glorify its owner, who can rest safe in the knowledge that his is the biggest.

What makes someone a good hi-fi reviewer? A fine critical sensibility? A good technical background? Ears? Eyes? Nose? Throat? So many different people are reviewing audio gear these days that it's downright impossible to characterize a good reviewer. But I do know that Beavis and Butt-head would make killer hi-fi reviewers!

There are two kinds of audiophiles: those who own original Quad ESL speakers and those who don't (footnote 1). This review is for the former, although the latter may find it of some interest. The Gradient SW-57 subwoofer attempts to do for the original Quad (footnote 2) what Gradient's SW-63 (footnote 3) does for the Quad ESL-63: supply the bottom octave while relieving the ESLs of the strain of reproducing low bass.

I should begin this review by confessing that I've never been a fan of subwoofers. Most subwoofer systems I've heard have been plagued by a familiar litany of sonic horrors: poor integration between subwoofer and main speakers, boom, bloat, tubbiness, slowness, excessive LF output, and an overall presentation that constantly reminds the listener he is hearing a big cone moving. To me, subwoofers often sound detached from the music, providing an accompanying thump that bears little relationship to the sound from the main speakers. Rather than revealing the music's harmonic underpinnings, subwoofers often obscure them in a thick morass of featureless boom. In addition, adding a subwoofer often destroys the qualities of the main speakers that made you buy them in the first placejust to name a few of my observations (footnote 1).

Velodyne introduced their series II subwoofer line in the fall of 1988, and it seems timely to review their largest, most powerful unit, the ULD-18. As the line's flagship, this Velodyne subwoofer represents the most sophisticated and expensive system offered by the company. It is sold as a system, complete with driver, enclosure, amplifier, control unit, electronic crossover, and servo cable and circuitry. Velodyne's unique servo circuitry, manufacturing techniques, and aggressive sales technique emanate from the company's designer, David Hall.

There was a time, as recently as 40 years ago, when frequencies below 100Hz were considered extreme lows, and reproduction below 50Hz was about as common as the unicorn. From our present technological perch, it's too easy to smirk condescendingly at such primitive conditions. But just so you're able to sympathize with the plight of these disadvantaged audiophiles, I should tell you that there were two perfectly good reasons for this parlous state of affairs. First of all, program material at that time was devoid of deep bass; not because it was removed during disc mastering but simply because there wasn't any to begin with. The professional tape recorders of the day featured a frequency response of 5015kHz, ±2dBjust about on a par with the frequency performance capability of a cheap 1988 cassette tape deck.

I was so impressed by the Nelson-Reed 8-04/B loudspeaker's low-end range that I seriously doubted the add-on subwoofers could add enough of significance to be cost-effective.

I was wrong.

Two of the subwoofers were provided, along with the necessary electronic crossover unit. Each 1204 unit contains four 12" woofers in a very solid sealed enclosure, with two facing to the front and two facing the rear. The electronic crossover has three controls, besides the AC power switch: a hardwire (footnote 1) bypass switch, a stereo/mono switch, and a subwoofer level control. In the stereo mode, the low frequencies are kept separate, left from right; in mono mode, they are blended together for feeding to a single subwoofer. I will not resurrect the question of whether or not it is important to maintain stereo separation into the LF range, except to echo N-R's observation that there is no LF separation on analog discs to begin with; the lows are mixed together, to limit vertical excursions of the cutting stylus that could cause it to rise above the disc surface or, worse, dig into the aluminum base of the master disc.